Fig. 1.

Schematic representation of the model, encompassing the time scale of self-organization (“work phase”) and the time scale of evolution (“selection phase”). At the start of each generation, M pairs of reproductives found colonies, each with N workers. The colonies go through a work phase where worker behavior is governed by the threshold model of division of labor: depending on whether task-specific stimuli are higher or lower than the genetically determined internal thresholds, workers will perform task 1, task 2, or do nothing. Each task-specific stimulus increases from one time step to the next, and it decreases again whenever a worker performs the task. After T time steps, colony fitness is determined as a function of the amount work performed and its distribution over tasks. Colonies produce reproductives proportionally to their fitness, and these individuals found new colonies, which will enter a new work phase